Most lumber used in the construction industry is known as dimension lumber, which the present invention is intended to use. Dimension lumber has opposite sides parallel, with adjacent sides forming a right angle, and is generally known by the nominal dimensions of the sides, e.g., 2×4, 2×6, 4×8, etc. The longer sides hereinafter are called “faces,” and the shorter sides are called “edges.” The pieces of dimension lumber to be processed by the present invention are called “workpieces” herein and, after cutting or processing, are called “components,” e.g., rafters of several kinds, and webs and chords for trusses.
There are three kinds of rafters with which the present invention is primarily concerned:                1. “regular” rafters:                    those which intersect their support or supported members, i.e. plates or ridge beams, respectively, at right angles to the faces, but at an angle to the edges thereof;                        2. “jack” rafters:                    those which, at one end, intersect at least one of their support or supported members at something other than a right angle to each of the faces and edges of the rafter, requiring a cut at what is called hereinafter a “compound” angle or a “bevel” cut on that end of the rafter; and                        3. “hip” and “valley” rafters:                    those which intersect their support or supported members where two or more come together at an angle, requiring two cuts on that end of the rafter, one or both of which may be compound angles. The angle at which the support or supported members come together is often, but not always, a right angle.FIG. 2 illustrates each of these kinds of rafters.                        
The present invention is also useful in cutting all of the webs and chords for a single truss in one operation. Typically, an individual component for a number of trusses was made up at the same time, to reduce the amount of hand adjustment, and therefore cost, per component. Otherwise, it became very expensive to produce them for a single truss, since adjustments had to be made between the cutting of each different component. Alternately, workpieces were fed into a cutting apparatus laterally, as opposed to linearly, as in the present invention. Lateral feed assemblies allow for simultaneous cutting of the ends of the workpieces, but are not as efficient where the saw blades must reset between each workpiece.
To lay out a roof structure, certain distances must be accurately known:                1. the distance between the outside edges of the double top plate;        2. the vertical distance from the upper face of the top-plate to the ridge line; and        3. the inclined, or slant, distance between the outside edge of the double top plates and the ridge line.        
It will help in understanding the following discussion to refer to FIGS. 1A-C of the drawings herein, which disclose three typical arrangements of rafters and their associated support or supported members, and will help to illustrate the concepts of “measuring line” and “ridge line”;                1. FIG. 1C discloses a rafter simply laid upon the double top plate and the ridge beam, without cutting the rafter, except perhaps for a small notch at the upper end where it rests on the ridge beam;                    a. the “measuring line” runs along the lower edge of the rafter, and            b. the “ridge line” is at the bottom of the rafter where it meets the adjoining or complementary rafter.                        2. FIG. 1B discloses a rafter notched at both upper and lower ends to fit over the ridge beam and the double top plate, respectively. In this case:                    a. the “measuring line” runs parallel to the rafter's lower edge, from the outer upper edge of the double top plates to the center line of the ridge beam above its upper edge; and            b. the “ridge line” is at the intersection of the two rafter measuring lines.                        3. FIG. 1A discloses a rafter cut at both upper and lower ends to rest against the face of the ridge beam and the upper face of the double top plate, and the lower edge of the rafter intersects the lower edge of the ridge beam and the inner edge of the double top plate. In this case:                    a. the “measuring line” runs parallel to the lower edge of the rafter, from the outer upper edge of the double top plates to the point of intersection of the measuring line with the face of the ridge beam; and            b. the “ridge line” runs down the midpoint of the ridge beam intersecting the projection of the measuring line.                        
The first structure of FIG. 1C is an older method of construction little used at the present time.
The second and third structures of FIGS. 1B AND 1A represent methods of construction which are more widely used at present.
Regular rafters, i.e., those on which the ends are cut at right angles to the faces (or the edges), even though the ends may be cut at something other than a right angle to the edges (or the faces, respectively), do not present a great problem to manufacture, since the length of a given rafter as measured on one face (or edge) is the same as the length measured on the other face (or edge).
However, hip, valley, and jack rafters present a more difficult problem of manufacture:                1. since jack rafters have at least one end thereof cut at a compound angle, i.e., an angle both to the edges and to the faces, the lengths of opposite faces (and/or edges) thereof are unequal; and        2. hip and valley rafters have at least one end which requires two cuts, both of which are at angles to the faces and edges, but which are usually at right angles to each other (although not necessarily). Although the lengths on the faces may be equal, the length on the measuring line will be different than both.        
Present machinery for making cuts to produce composite or compound angles on roof structure components still requires substantial hand labor in the set-up and/or operation of cutting equipment.
U.S. Pat. No. 4,545,274 teaches a means of tilting the axis of travel of a saw blade to correspond to the complement of the roof slope, and then angling the saw blade to make the compound cut. Lumber is moved past the cutting station in a sideways manner. A separate cutting station is required for cuts on the other end of the component and, to cut components of differing lengths, one of the cutting stations must be movable in relation to the other, which takes time. Further, the cutting process is not automatic.
U.S. Pat. No. 6,212,983 incorporated herein by reference, teaches a linear feed system where compound cuts are achieved by tilting the work surface supporting the workpiece. This requires automating and adjusting the work surface to be movable for compound cuts. Adjusting workpieces of great length may prove cumbersome. An example of a lateral feed assembly can be found in Shamblin, U.S. Pat. No. 5,943,239, which is incorporated herein. Such a system employs four or more cutters and requires more work space and added expense.
There is no known linear feed machinery presently available to sequentially and automatically make the cuts necessary to achieve compound angles.